This invention relates to improvements in the mechanized sampling of bulk materials. In particular, to a system for taking a cross-stream sample of bulk materials from a conveying line.
The invention was primarily developed for use in the incremental collection of samples of coal from a conveyor line, and it is therefore convenient to describe the same as used for such purposes. Of course, the invention may be used in the sampling of various bulk materials and is not to be in any way construed as limited to the sampling of such as coal and coke.
It is apparent that a coal user wants and expects that coal shipped to him by a supplier have certain characterisitcs as to size, combustion, moisture content, BTU output, etc., in accordance with the needs of the user. Thus, a supply contract may provide for representative sampling of the coal shipment by the supplier, at the source, and by the user, on delivery. Since the respective sampling occurs at different times, at different places, and frequently according to different procedures, there is sometimes disagreement between the user and supplier as to the representative nature of the samples taken by the supplier. It would obviously be mutually advantageous for the user and supplier to agree upon use of a particular sampling system that would be accepted by the user as providing a representative sampling of the coal shipment.
Coal is one of the most difficult of materials to sample, a given conveying stream thereof including both small and large lumps, of various size and shape, down to dust size particles, and of varying composition, from particles that are noncombustible to those which can be burned completely.
Coal sampling is made even more difficult in that belt conveyors are most usually used for the conveying lines of coal handling facilities. The conveyor belt of such belt conveyors is typically supported on a plurality of spaced apart three roll idlers. The conveying surface of the conveyor belt thus presents faces that are angled with respect to one another and, since such belts are flexible, they will flex under sampling sweep arm pressures, making it difficult to remove a complete cross-stream sample therefrom. Also, since the belts of such belt conveyors have limited impact load capabilities, a sweep arm moving cross-stream for taking of a sample therefrom has a tendency to impact against and drive coal segments into the belt in a manner likely to puncture the belt.
An object of this invention is the provision of a contour means for modulating the normal troughing of a conveyor belt and supporting and conforming the same for facile removal of a cross-stream increment of bulk material therefrom.
The American Society for Testing Materials (ASTM), a recognized standards authority, provides certain designations to be used for sampling specifications, as follows:
Types of Increments:
Type I, in which specific pieces or portions are not subject to selection on a discretionary basis;
Type II, in which some measure of human discretion is exercised in the selection of specific pieces of coal or of specific portions of the stream, pile, or shipment;
Conditions of Increment Collection:
Condition A (Stopped-Belt Cut), in which a loaded conveyor belt is stopped and a full cross-section cut with parallel sides is removed from the coal stream. The distance between the parallel faces shall not be less than three times the diameter of the largest piece.
Condition B (Full-Stream Cut), in which a full cross-section cut is removed from a moving stream of coal.
Condition C (Part-Stream Cut), in which a portion, not a full cross stream, is removed from a moving stream of coal.
Condition D (Stationary Coal Sampling), in which a portion of coal is collected into a pile, a rail car, a barge, or a shiphold.
Spacing of Increments:
Systematic Spacing, in which the movements of individual increment collection are spaced evenly in time or in position over the lot.
Random Spacing, in which the increments are spaced at random in time or in position over the lot.
The ASTM specifies that the best possible increment is a full cross-section cut removed from a stopped belt. That is, a "Type I" increment, collected according to "Condition A", at "Systematic Spacing" intervals.
I am aware that others have provided various apparatus for sampling of bulk materials from a conveying line. For instance, as shown by U.S. Pat. No. 2,889,709, a "Condition C" increment collection; U.S. Pat. No. 3,280,635, a "Condition C" increment collection; U.S. Pat. No. 3,487,427, which does not appear to fall within any ASTM condition of increment collection; U.S. Pat. No. 3,791,218, a "Condition C" increment collection; and U.S. Pat. No. 4,133,210, a "Condition C" increment collection.
Until development of the present invention, all mechanized samplers have been of the ASTM "Condition B" or "Condition C" categories. I do not know of any previously provided mechanized stopped belt sampler according to the ASTM "Condition A".
Accordingly, a further object of this invention is the provision of a system for the mechanized sampling of bulk materials from a stopped belt conveyor in which the specific pieces or portions are not subject to selection on a discretionary basis; in which the loaded conveyor belt is stopped and a full cross-section cut with parallel sides is removed from the conveyor stream; and in which the movements of individual increment collection are spaced evenly in time or position over the lot.
Belt conveyors in use by coal handling facilities run from a length of less than a hundred feet to more than a thousand feet, the belt width of which may be from eighteen to ninety-six inches, and the belt speed of which may be from approximately four hundred feet per minute to approximately a thousand feet per minute. It is obvious that it would not be practical to intermittently stop a lengthy high-capacity belt conveyor for sampling purposes. Thus, as a mechanized stopped belt sampler, my invention will generally be used in connection with belt conveyors having a length of one hundred feet or less and having a belt width of forty-two inches or less.
My invention may also be adapted for taking a "Condition B" sample, that is, one in which a full cross-section cut is removed from a moving stream.
Other objects and advantages of the invention will become apparent from the following detailed description, taken in connection with the accompanying drawings, and in which drawings: